Problem: William ate 5 slices of cake. Kevin ate 4 slices. If William ate $\dfrac{5}{10}$ of the cake, what fraction of the cake was eaten?
Solution: If 5 slices represent $\dfrac{5}{10}$ of the cake, there must have been a total of 10 slices. $\text{fraction of cake eaten} = \dfrac{\text{number of slices eaten}}{\text{number of slices total}}$ They ate ${9}$ out of $10$ slices. They ate $\dfrac{9}{10}$ of the cake.